Safety paper



Patented July 23, 1940 PATENT OFFlCE SAFETY PAPER William Whitehead,Cumberland, Md., assig'nor to Celanese Corporation of America, acorporation of Delaware No Drawing. Application September 16, 1937,

Serial No. 164,126

- ent invention is that the threads may be dissolved 8 Claims.

This invention relates to identifiable paper and other cellulosicmaterials, and to the process of making the same, wherein the mark ofidentification comprises fibers which are fluorescent in ultra-violetlight, soluble in solvents that have no eflect on the cellulosic fibersand capable of being colored so that they are completely fast to acids,aikalies, bleaching agents, etc.

An object of the invention is the economic and expeditious production ofcellulosic materials, such as paper, cardboard, felts, etc., which haveincorporated therein fluorescent fibers, made of or containing anorganic ester of cellulose, as a mark or means of identification or as adecoration. A still further object of this invention is the productionof paper to be used as banknote paper, stock certificates, revenuestamps, labels and the like, the authenticity of which paper may bedetermined by a plurality of simple tests since the paper containsfibers which are fluorescent in ultra-violet light or near ultravioletlight and which fibers may be dissolved out of the paper by means ofsolvents which have no efi'ect upon the fiber and since the fibers mayhave one or a plurality of definite diameters.

Identifiable paper, as heretofore commonly manufactured, hadincorporated therein short lengths of silk fibers as a means ofidentification. This paper has been used mostly as bank-note or currencypaper. The silk fibers are of two-fold importance, firstly, for thereason that they show the paper to be of a certain type and, secondly,because colored fibers in the paper make more diflicult the photographicreproduction of printed matter on the paper. I have found that byincorporating in paperfibers made of or containing anorganicester ofcellulose that has-been treated with a tertiary amine, there areobtained many advantages which are not obtainable with paper employingsilk fiber. One advantage of employing an organic ester of cellulosetreated with tertiary amine, which gives to the organic ester ofcellulose the property of being fluorescent .in ultra-violet and nearultra-violet light, is that photographic reproductions with variouscolor filters becomes more diflicult. Another advantage of employingsuch fibers is that,there may be incorporated in the paper several typesof fibers, that is, fibers having difierent denier, different color anddiflerent composition, and the fibers may be present in variousproportions, some or all of which are fluorescent, such that upon amicroscopic examination of'the paper in various lights the authenticityof the same is easily ascertained. Another advantage or the presfrom thepaper without effecting the paper, thus giving rise to a very simpletest for the authenticity of the paper. Furthermore, by employing thisinvention, identification marks may be made resistant to or unefiectedby bleaching agents, or the paper may have some identification markswhich cannot be removed by a bleaching operation and others which can beremoved by a bleaching operation. 10

In accordance with my invention, I form sheet cellulosic material, suchas tissue paper, writing paper, cardboard or other types of materialfrom any suitable cellulosic material and incorporate in said cellulosicmaterial fibers, formed of or containing an organic ester of celluloseand a tertiary amine having at least two aryl substitution groups, ofany desired denier, color, length, or' mixtures of such fibers. Thefibers made from or containing an organic ester of cellulose may beincorporated in the cellulosic material in any suitable manner. However,in accordance with this invention, I prefer to incorporate the organicester of cellulose treated with the tertiary amine in the paper stock orpulp, either before the beater or before or after the Jordan, by feedingto the stock a uniform amount of the fibers. This may be accomplished byfeeding a lap or roving formed of organic ester of cellulose fibers tothe paper stock or by forming a suspension of the said fiber and flowingit into the paper stock.

The base material of the paper or other cellulosic article may be anysuitable stock normally employed in the formation of such cellulosicarticles. For instance, the paper or other cellulosic article may bemade from wood or vegetable pulps made by the mechanical method, sodamethod, sulphate method, sulphite method or combinations of these, orfrom cotton and linen rags or o masticated paper or mixtures of these.The paper or other cellulosic article may be formed on the samemachinesand in the same manner as such articles have been previouslymanufactured. For instance, this invention is applicable 5 to handmethods of making paper, cardboard and the like or to the machinemethods wherein the pulp is mixed, then passed through a beater,

a Jordan, blending tanks and onto a sluiceway to the screens or to theFourdrinier. The paper or other cellulosic article may be of anysuitable thickness from tissue paper up to felts and blocks. Thisinvention is of particular importance, however, with cellulosic articlesof writing paper thickness or wall paper thickness. This invenbutyrate.

tion, moreover, is of some importance in the manufacture of cardboardfor containers as the identifiable characteristic of the same makespossible the ready detection of counterfeit or spurious packages.

As stated, this invention relates to the production of identifiablepaper or other cellulosic materials that are to be used for any purposewhere ready identification is desirable. This invention is also ofimportance in the manufacture of cardboard for boxes or closure membersof containers, for pass cards and the like. In the above applications ofthe invention the problem of ready identification and the difficulty ofduplicatior is of major importance.

The invention, however, has also another object, i. e. that ofdecoration. In the above applications of the invention the decorativefeature may be incorporated along with the protective feature, or theinvention may be used purely for decorative effects in, for example,tissue paper either of the soft or glazed variety used as wrappings forbottles, packages, and, in fact, articles of all kinds. Here also theprotective feature may be of some importance in that each manufacturermay have a particular color, denier or mixtures of colors and denierswhich make the origin of the wrappings easily determinable. Thisinvention may be used in the production of wall paper, coverings forindividual packages or boxes and the like. For instance, I may producepaper, such as wall paper, or coverings for cardboard boxes, byemploying a mixture of organic ester of cellulose fibers and printing ordyeing the organic ester of cellulose fiber after it is in the paper.Wall paper made 'in accordance with my invention may include organicester of cellulose fibers of different color, denier and pigmentation,as well as organic ester of cellulose fiber of natural color. A designmay be printed on the paper by employing dyes having affinity forcellulose fiber and no aflinity for an organic ester of cellulose fiberand/or dyes having affinity for organic ester of cellulose fiber onlyand not for cellulosic materials. Multiple color effects in paper arethus produced through a differential dyeing or printing operation andthrough the pigment or coloring matter already in the organic ester ofcellulose fibers. This differential or multiple color effect coupledwith the fluorescent property of the treated organic ester of cellulosefibers would be impos- 'sible to duplicate without starting with theformation of the paper and then only when the percentages of the variouscomponents are known.

Any suitable type of organic ester of cellulose fiber may be employed inmaking identification marks in or on the cellulosic material, forinstance, fibers formed'of cellulose acetate or other organic esters ofcellulose, such as cellulose formate, cellulose propionate and celluloseThe organic ester of cellulose fibers may be formed by spinning into theform of substantially continuous filaments a solution of an organic wetmethod of spinning. The substantially continuous filaments as individualfilaments,

bands, bundles or hanks, may then be cut or torn into suitable lengths.

The fibers incorporation in the ccllulosic article may be of anysuitable length, for instance, from :32 of an inch to 3 or more inches.The organic ester of cellulose fibers may be relatively straight or thesame may be embossed or treated in liquids to impart to the fiber acurl, print or other configuration. If desired, the fibers, orfilaments, before being cut or torn into fibers, may be intermittentlyembossed by such means as heated embossing rolls to form segments whichhave a predetermined configuration, while other segments have theirnatural fiber-like shape. As the organic ester of cellulose fibers arethermoplastic, this embossing is permanent and the configuration is moreor less carried into the finished article regardless of the drasticaction in the Jordan and sluiceway.

The organic ester of cellulose fiber may contain, besides the organicester of cellulose base material and the tertiary amine, eifectmaterials such as pigments, plasticizers, dyes, lakes, fillingmaterials, fire retardants and the like. These materials may beincorporated in the fibers by adding the effect materials to thesolution of organic ester of cellulose prior to its formation intofilaments, or the effect materials may be added to the formed filamentsor fibers in any suitable manner. For instance, the fibers may be dyedby means of dye baths with or without the aid of swelling agents and thelike. Pigmented fibers are of exceptional value for identificationpurposes. The pigmented fibers may be of any suitable color from whiteto black. They may be formed by mixing with the spinning solution fromwhich the fibers are formed such pigments as the metal oxides,hydroxides, carbonates, phosphates, etc. For instance, a white fiber maybe formed by incorporating titanium, zinc or lead oxide in a fiber,while red fibers may be produced by incorporating iron oxide or the likein a fiber, while blue fibers may be formed by incorporating Prussianblue therein. Besides the metal oxides, hydroxides or metal salts, theremay be employed as pigments insoluble or relatively insoluble organiccompounds.

The fibers of an organic derivative of cellulose employed in themaking-of the ccllulosic materials may be of any suitable denier, or amixture of fibers of different deniers may be used. For instance, fibershaving a denier of 0.3 up to 20 or more may be employed or mixtures offibers of any desired deniers may be employed. In the manufacture of theorganic derivative of cellulose fiber by means known in the art, thefibers may be made to have a denier which varies in any desired amountover a given length. When these fibers are cut into the length desiredin the finished paper, the fibers show this varying denier which givesrise to a still further means of determining the origin of a paper. Instamps, stock certificates, currency and the like it is often desirableto incorporate in the ccllulosic base material a low denier fiber, s91.fiber having a denier of 0.5, as a means of making difflcult thephotographic reproduction of the article, and then large denier fibers,say 3'to 10 denier, for a ready or more visible determination of theauthenticity of the article. The fibers of the same denier or of eachdenier may be of the same or of a diiferent color.

The fibers of an organic derivative of cellulose may be dyed anysuitable color prior to incorporation in the cellulosic material or thefibers may be of natural color. I have found that organic derivative ofcellulose fiber containing a white or colored pigment is of exceptionalvalue in this respect in that the color of the fiber is unaffected byacids, alkalies, bleaching agents and the like, although the fiber mayreadily be dissolved by solvents such as acetone, chloroform, ethyldichloride, a mixture of diethylene chloride and ethyl or methyl alcoholand the like. Thus, by placing the cellulosic material or paper in thesolvent, there is provided a ready test as to whether the identifiablefibers are formed of an organic ester of cellulose or not, whereasplacing the cellulosic material in a bleaching agent is a ready test asto whether the fibers are pigmented or dyed. The organic.

ester of cellulose fibers may be partially saponified or intermittentlysaponified, whether they be pigmented or not, to change their amnity forprinting inks, dyes, etc. The use of the intermittently saponifiedfibers gives rise to still another possibility of identifying the originof the certain cellulosic material since the saponified segment of thefiber of identification can be dissolved only by the use of solventsdifierent from those which are capable of dissolving the other segment.

Fibers other than organic esters of cellulose which have been treatedwith a tertiary amine such as, for example, benzyl ethyl aniline do notfiuoresce in near ultra-violet light. erty is particular to the organicesters of cellulose. Therefore, by intermittently saponifying fibers oforganic esters of cellulose a single colored fiber may be made tofiuoresce on one portion of its length and not on another portion of itslength.

Thus, in accordance with my invention, the origin of the cellulosicmaterial is ascertained by easy and simple tests such as the characterof fluorescence in ultra-violet or near ultra-violet light, the size ofthe identification fibers, the number of different sizes or whether thefibers are bleach-proof or easily bleached. For instance, there may beplaced in a paper different types of fibers, such as large denierfibers, small denier fibers having a curl or a crimp to interfere withphotographic reproductions or, say, a black fiber unaffected bybleaching mixed with red fibers easily bleached, some or all of thesefibers being fluorescent, or any other combination of fibers describedabove.

The fluorescent property may be imparted to the organic ester ofcellulose fiber by incorporating with the fiber a small amount of a.tertiary amine having at least two aryl substitution groups. Examples ofsuch tertiary amines are besides the benzyl ethyl aniline noted above,dibenzyl aniline, benzyl phenyl aniline, phenyl ethyl aniline, etc.After incorporating the tertiary amine with the organic ester ofcellulose the same is subjected to ultra-violet light for from 5 to 60minutes after which period it' becomes fluorescent and this property ispermanent. The organic esters of cellulose absorb these tertiary aminesand, therefore, the tertiary amine may be incorporated with the yarn.during the dyeing operation where the tertiary amine is in suspension orin a dispersion of the dye bath. The tertiary amine may be incorporatedwith the fibers by mixing the same with an oily substance andlubricating the fibers with this mixture during a winding operationor'by batching the material in a bath of the same. The tertiary aminemay also be incorporated with the organic ester This propof cellulosefiber by applying the same to the organic ester of cellulose prior toforming it into filaments or fibers. Thus, the tertiary amine may beadded to the stabilizing bath in the preparation of the organic ester ofcellulose or the tertiary amine may be added to the spinning solution.Any amount of the tertiary amine may be employed, for instance, from0.05% to 10% or .more based upon the weight of the organic ester ofcellulose fiber, the preferred amount being from 0.3% to 1%.

The organic ester of cellulose fiber may be incorporated in the paper inany suitable manner. However, I have found it of advantage to form theorganic ester of cellulose fiber into a sliver of fairly uniform weight.By this means where more than one type of organic ester of cellulosefiber is employed the proper distribution or mixing of the product iseasily obtained. This sliver whether in spool form or canned is drawn tothe stream of paper stock either before it enters the Jordan or after ithas passed through the Jordan prior to reaching the screens and there itis broken down into the individual filaments by' means of water jets,beaters, air or other means and mixed into the paper stock.

In place of forming the fibers into a roving, I may form the fibers oforganic ester of cellulose into a lap by means of a cotton or woolcarding device. a point above a flowing stream of paper stock and bymeans of heaters, air jets or other means broken down to the individualfibers, and the fibers forced into the stream of paper stock passingtherebeneath. If it is desired to placethe marks of identification onlyon predetermined sections of the paper, this may be done by feed- 'ingthe organic ester of cellulose fiber to the paper stock where the paperstock meets the screens. Here the organic ester of cellulose fibers maybe fed to the paper stock in rows, bunches or otherwise. i

I have also found that the organic ester of cellulose fiber may be mixedwith the paper stock by forming a slop of the organic ester of cellulosefiber in water by the addition of from 1 to 5% on the weight of organicester of cellulose fiber of tapioca, starch, dextrin and the like.Tapioca, starch, dextrin and the like gives to the mixture of water andorganic ester of cellulose fibers suflicient. body and viscosity so thatthe This lap is pulled between nip rolls to which are left in the tank.Tapioca, starch and dextrin also act as a protective colloid for thefibers.

Any suitable percentage of organic ester of cellulose fibers may bemixed with the cellulosic fiber stock. A suitable amount for stock.certificates, bonds and revenue stamps, when employing a dark coloredfiber, is a 5 denier organic ester of cellulose fiber in an amount equalto about 1 to 4% based on the weight of the cellulosic fiber. Obviously,smaller or greater percentages of each may be employed accordingto theresult desired. In the manufacture of wall paper, coverings forcardboard or the cardboard boxes themselves as high as 20 to 30% o'f or-As an illustration of this invention, but without being limited thereto,the following example is given:

Example By means of a cotton card a lap is formed from denier celluloseacetate fibers containing 0.5% on the weight of the fibers of benzylethyl aniline. A slurry of a sulphite wood pulp containing about oflinen or rag pulp is formed in the usual manner. To the stream ofsulphite pulp fiowing from the Jordan onto the screen is added thecellulose acetate fiber in an amount equal to 3% on the weight of theair dried paper. The addition of the cellulose acetate fiber to thestream of sulphite pulp is accomplished by drawing the lap through niprollers at a constant speed to give the desired percentage of fibers andbeating with mechanical beaters the end of the lap as it comes throughthe nip rollers in a manner to knock the fibers free from each other andinto the stream of sulphite pulp. The fiber is found to have thecellulose acetate fibers evenly dispersed therein. The cellulose acetatefibers are readily visible, individually fluorescent in ultra-violetlight, and may be dissolved from the paper by dipping the paper inacetone. There is no tendency for the paper at those parts notcontaining cellulose acetate fiber to fiuoresce.

It is to be understood that the foregoing de tailed description ismerely given by way of illustration and that many variations may be madetherein'without departing from the spirit of my invention.

Having described my invention, what I desire to secure by Letters Patentis:

1. A safety paper comprising a felted body of cellulose fibers andhaving embedded therein from 1 to 4%, based on the weight of thecellulose fibers, of organic ester of cellulose fibers containing benzylethyl aniline.

2. A safety paper comprising a felted body of ce1lulose fibers andhaving embedded therein from 1 to 4%, based on the weight of thecellulose fibers,

of cellulose acetate fibers containing benzyl ethyl aniline.

3. A safety paper comprising a felted body of cellulose fibers andhaving embedded therein from 1 to 4%, based on the weightof thecellulose fibers, of organic ester of cellulose fibers containing 5%,based on the Weight of the organic ester of cellulose fibers, of benzylethyl aniline.

4. A safety paper comprising a felted body of cellulose fibers andhaving embedded therein from 1 to 4%, based on the weight of thecellulose fibers, of cellulose acetate fibers containing based on theweight of the cellulose acetate fibers, of benzyl ethyl aniline.

5. A safety paper comprising a felted body of cellulose fibers andhaving embedded therein 3%, based on the weight of the cellulose fibers,of organic ester of cellulose fibers containing based on the weight ofthe organic ester of cellulose fibers, of benzyl ethyl aniline.

6. A safety paper comprising a felted body of cellulose fibers andhaving embedded therein 3%, based on the weight of the cellulose fibers,of cellulose acetate fibers containing /2%, based on the weight of thecellulose acetate fibers, of benzyl ethyl aniline.

7. A safety paper comprising a felted body of cellulose fibers andhaving embedded therein from 1 to 4%, based on the weight of thecellulose fibers, of organic ester of cellulose fibers, said organicester of cellulose fibers-being a mixture of such fibers having at leasttwo deniers, at least two colors and at least one component thereofcontaining benzyl ethyl aniline.

8. A safety paper comprising a felted body of cellulose fibers andhaving embedded therein from 1 to 4%, based on the weight of thecellulose fibers, of cellulose acetate fibers, said cellulose acetatefibers being a mixture of such fibers having at least two deniers, atleast two colors and at least one component thereof containing benzylethyl aniline.

. WILLIAM WHITEHEAD.

